The inventors know of several references which disclose laundering processes conducted at a washing temperature roughly equal to the cloud point temperature of the washing liquor, but none of these references appears to teach washing substantially above the cloud point temperature, yet below the phase coalescence temperature. For example, U.S. Pat. No. 3,707,506, issued to Lozo on Dec. 26, 1972, suggests at Col. 1, lines 44-54, that there is some error in the prior art belief that maximum efficiency in removing dirt with a nonionic washing liquor is obtained at temperatures below the detergent cloud point. The Lozo reference does not provide any positive teaching, however, as to what washing temperature may be selected to improve washing results. An article by Cook entitled "Versatility of Nonionic Detergents" published in Soap and Chemical Specialties, May 1955, pages 47-49, indicates that a nonionic detergent works best if its surface active agent is not completely dissolved, but rather is partially in a colloidal state which promotes micelle formation. U.S. Pat. No. 3,925,224, issued to Winston on Dec. 9, 1975, similarly teaches that a cloudy solution of a surfactant is optimal for laundering fabrics. It is believed that the Cook and Winston references essentially describe washing at the cloud point temperature of the washing liquor rather than at a temperature substantially above the cloud point temperature.
Two references have been found which provide teachings contrary to the present development, indicating that it is undesirable to wash at or above the cloud point temperature. These references are: U.S. Pat. No. 3,890,238, issued to Boehmer on June 17, 1975; and Colwell et al., "Considerations in the Use of Nonionic Surface Active Agents," American Dye Stuff Reporter, Vol. 50, Sept. 4, 1961, 39 (cumulative page 679).
British Patent Specification No. 1,518,676, naming Mould et al. as inventors and published July 19, 1978, teaches washing substantially above the phase coalescence temperature of the washing liquor, but not within the temperature range between the cloud point and phase coalescence temperatures.
The prior art teaches that it is known to add a strong electrolyte to an aqueous solution containing a nonionic surfactant in order to lower the cloud point of the solution. For example, see Schick, Nonionic Surfactants, Marcel Dekker, Inc. (NY, 1966), Library of Congress Cat. Card No. 66-22492, especially pages 572-573.
Numerous prior art references can be found which generally indicate that a nonionic detergent may be combined with a builder, a strong electrolyte, or mixtures thereof to form washing compositions. However, no such disclosures are known which reveal compositions having the relatively narrow ranges of proportions of strong electrolytes and builders which are necessary to realize the present improvement at specific temperatures which are typical in the field of commercial laundering.